io_uring: track mm through current->mm

As a preparation for extracting request init bits, remove self-coded mm
tracking from io_submit_sqes(), but rely on current->mm. It's more
convenient, than passing this piece of state in other functions.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8153247..f7825d3 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5812,8 +5812,7 @@ static void io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 }
 
 static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
-                         struct file *ring_file, int ring_fd,
-                         struct mm_struct **mm, bool async)
+                         struct file *ring_file, int ring_fd, bool async)
 {
        struct io_submit_state state, *statep = NULL;
        struct io_kiocb *link = NULL;
@@ -5870,13 +5869,12 @@ fail_req:
                        break;
                }
 
-               if (io_op_defs[req->opcode].needs_mm && !*mm) {
+               if (io_op_defs[req->opcode].needs_mm && !current->mm) {
                        if (unlikely(!mmget_not_zero(ctx->sqo_mm))) {
                                err = -EFAULT;
                                goto fail_req;
                        }
                        use_mm(ctx->sqo_mm);
-                       *mm = ctx->sqo_mm;
                }
 
                req->needs_fixed_file = async;
@@ -5902,10 +5900,19 @@ fail_req:
        return submitted;
 }
 
+static inline void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
+{
+       struct mm_struct *mm = current->mm;
+
+       if (mm) {
+               unuse_mm(mm);
+               mmput(mm);
+       }
+}
+
 static int io_sq_thread(void *data)
 {
        struct io_ring_ctx *ctx = data;
-       struct mm_struct *cur_mm = NULL;
        const struct cred *old_cred;
        mm_segment_t old_fs;
        DEFINE_WAIT(wait);
@@ -5946,11 +5953,7 @@ static int io_sq_thread(void *data)
                         * adding ourselves to the waitqueue, as the unuse/drop
                         * may sleep.
                         */
-                       if (cur_mm) {
-                               unuse_mm(cur_mm);
-                               mmput(cur_mm);
-                               cur_mm = NULL;
-                       }
+                       io_sq_thread_drop_mm(ctx);
 
                        /*
                         * We're polling. If we're within the defined idle
@@ -6014,7 +6017,7 @@ static int io_sq_thread(void *data)
                }
 
                mutex_lock(&ctx->uring_lock);
-               ret = io_submit_sqes(ctx, to_submit, NULL, -1, &cur_mm, true);
+               ret = io_submit_sqes(ctx, to_submit, NULL, -1, true);
                mutex_unlock(&ctx->uring_lock);
                timeout = jiffies + ctx->sq_thread_idle;
        }
@@ -6023,10 +6026,7 @@ static int io_sq_thread(void *data)
                task_work_run();
 
        set_fs(old_fs);
-       if (cur_mm) {
-               unuse_mm(cur_mm);
-               mmput(cur_mm);
-       }
+       io_sq_thread_drop_mm(ctx);
        revert_creds(old_cred);
 
        kthread_parkme();
@@ -7507,13 +7507,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                        wake_up(&ctx->sqo_wait);
                submitted = to_submit;
        } else if (to_submit) {
-               struct mm_struct *cur_mm;
-
                mutex_lock(&ctx->uring_lock);
-               /* already have mm, so io_submit_sqes() won't try to grab it */
-               cur_mm = ctx->sqo_mm;
-               submitted = io_submit_sqes(ctx, to_submit, f.file, fd,
-                                          &cur_mm, false);
+               submitted = io_submit_sqes(ctx, to_submit, f.file, fd, false);
                mutex_unlock(&ctx->uring_lock);
 
                if (submitted != to_submit)